The left ventricular-aortic bypass composite prosthesis has been developed to provide relief of left ventricular hypertension in certain patients with congenital and acquired forms of aortic stenosis. The shunt consists of an inflow portion (titanium tube) and a Dacron graft containing a glutaraldehyde-preserved xenograft valve. Problems in these studies have included the development of xenograft valve regurgitation due to improper support of the valve commissures within the graft conduit. Valve struts and a frame have not been employed when the porcine valve is used in this fashion, so that poor coaptation of the cusps could develop in time following implantation in calves. A second problem to be solved involved detachment of the fibril interface from the titanium inflow tube section of the composite prosthesis. Efforts to eliminate the problem of xenograft valve regurgitation have centered around the use of Teflon bolsters in the commissures of the valve. Fibril embolization was stopped by replacing the polyester fibrils in the metal inflow tube. This latter interface was changed to a porous metal surface which functions in a similar manner but is firmly fused to the underlying metal tube to prevent surface dislodgement. Studies will continue during this third year of the program to improve the composite shunt in animals evaluated for periods of up to twelve months' duration.